Substance detection sensor

ABSTRACT

A substance detection sensor includes an insulating layer; two electrodes spaced in opposed relation to each other on the insulating layer; and conductive layers formed between the two electrodes on the insulating layer so as to electrically connect the two electrodes, and of which a swelling ratio varies depending on the type and/or amount of a specific gas. The conductive layers are formed by dividing into plural layers between the two electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional patent application of U.S. patentapplication Ser. No. 12/654,483 filed Dec. 22. 2009, which claimspriority from Japanese Patent Application No. 2009-5091, filed Jan. 13,2009, the content of all of which are herein incorporated by referencein their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substance detection sensor, and moreparticularly to a substance detection sensor for mainly detecting thetype or amount of gas.

2. Description of Related Art

Heretofore, material sensors for detecting gas or liquid have been usedin various industrial applications. The material sensor is used forqualitative and quantitative analysis of specific gases or liquids.

For example, there have been proposed sensor arrays including a resistorcontaining a conductive substance, and first and second conductive leadsspaced apart from each other and electrically coupled via the resistor(cf. Japanese Unexamined Patent Publication No. 2006-10703).

In the sensor arrays of Japanese Unexamined Patent Publication No.2006-10703, the resistor is formed by applying (casting) a solutioncontaining a conductive substance so as to contact the first and thesecond conductive leads, and then drying the solution.

SUMMARY OF THE INVENTION

However, in Japanese Unexamined Patent Publication No. 2006-10703, sincethe solution is applied onto the first and the second conductive leadsto collectively form the resistor at a time, the resistor may be formedin uneven thickness. In particular, when the resistor is formed to havea large area, it may have a considerably uneven thickness.

As a result, the sensor cannot accurately detect a substance due to theuneven thickness of the resistor.

It is an object of the present invention to provide a substancedetection sensor capable of detecting a substance with excellentaccuracy by forming a conductive layer in uniform thickness.

The substance detection sensor of the present invention includes aninsulating layer; two electrodes spaced in opposed relation to eachother on the insulating layer; and a conductive layer formed between thetwo electrodes on the insulating layer so as to electrically connect thetwo electrodes, and of which a swelling ratio varies depending on thetype and/or amount of a specific gas, the conductive layer being formedby dividing into plural layers between the two electrodes.

According to the substance detection sensor of the present invention,the conductive layers are formed by dividing a layer into plural layers,so that each of the conductive layers has a small area. This allows thethickness of the respective conductive layers to be made uniform.Therefore, the thickness of the entire conductive layer can be madeuniform.

As a result, the substance detection sensor can detect a substance withexcellent accuracy.

It is preferable that the substance detection sensor of the presentinvention includes wires for connecting the conductive layers formed bydividing into plural layers, and it is further preferable that theconductive layers formed by dividing into plural layers are spaced apartfrom each other, and the wires are connected to the respective adjacentconductive layers, or it is preferable that the conductive layers formedby dividing into plural layers include an overlapping portion overlappedeach other, and the wires are connected to the respective adjacentconductive layers so as to sandwich the overlapping portion.

In the substance detection sensor, since the conductive layers formed bydividing a layer into plural layers and spaced apart from each other areconnected between a pair of electrodes through the wires, the connectionbetween the pair of electrodes can be ensured, which in turn canreliably perform substance detection with high accuracy.

Alternatively, in the substance detection sensor, since the. conductivelayers formed by dividing a layer into plural layers and including theoverlapping portion is connected between the pair of electrodes throughthe wires, the connection between the pair of electrodes can be ensured,which in turn can reliably perform substance detection with highaccuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a gas detection sensor as an embodiment of asubstance detection sensor according to the present invention;

FIG. 2 is a sectional view taken along the line A-A of FIG. 1;

FIG. 3 is a process diagram showing a method for producing the gasdetection sensor shown in FIG. 2;

(a) showing the step of preparing an insulating layer,

(b) showing the step of forming an electrode pattern and a bridge wire,

(c) showing the step of forming a protective layer, and

(d) showing the step of forming conductive layers;

FIG. 4 is a plan view of another embodiment (an embodiment in whichthree conductive layers are provided) of the gas detection sensoraccording to the present invention;

FIG. 5 is a plan view of another embodiment (an embodiment in which abridge wire is formed in a generally rectangular shape in plane view) ofthe gas detection sensor according to the present invention;

FIG. 6 is a plan view of another embodiment (an embodiment in which abridge wire is formed in a generally rectangular frame shape in planeview) of the gas detection sensor according to the present invention;

FIG. 7 is a plan view of another embodiment (an embodiment in which abridge wire is formed in a generally rectangular frame shape in planeview) of the gas detection sensor according to the present invention;

FIG. 8 is a plan view of another embodiment (an embodiment in which abridge wire is formed in a generally H-shape in plane view) of the gasdetection sensor according to the present invention;

FIG. 9 is a plan view of another embodiment (an embodiment in which twoconductive layers are in contact with each other) of the gas detectionsensor according to the present invention;

FIG. 10 is a sectional view taken along the line B-B of FIG. 9;

FIG. 11 is a plan view of another embodiment (an embodiment in whichconductive layers have an overlapping portion) of the gas detectionsensor according to the present invention;

FIG. 12 is a sectional view taken along the line C-C of FIG. 11; and

FIG. 13 is a plan view of the gas detection sensor (an embodiment inwhich one conductive layer is continuously formed) of ComparativeExample 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a plan view of a gas detection sensor as an embodiment of asubstance detection sensor according to the present invention, FIG. 2 isa sectional view taken along the line A-A of FIG. 1, and FIG. 3 is aprocess diagram showing a method for producing the gas detection sensorshown in FIG. 2. Incidentally, the directions are described withreference to FIG. 1, that is, the left side, the right side, the lowerside, the upper side, the near side, and the far side of the paper planewill be referred to as the “front side”, “rear side”, “right side” (oneside), “left side” (the other side), “upper side”, and “lower side”,respectively.

In FIGS. 1 and 2, the gas detection sensor 1 includes an insulatinglayer 2, an electrode pattern 3 formed on the insulating layer 2, abridge wire 9 serving as wiring formed on the insulating layer 2, and aconductive layer 4 formed on the insulating layer 2 so as to beelectrically connected with the electrode pattern 3 and the bridge wire9.

The insulating layer 2 is formed, for example, from a sheet having agenerally rectangular shape in plane view.

The electrode pattern 3 includes a pair of electrode wires 6 on theupper surface of the insulating layer 2. The pair of electrode wires 6is spaced in opposed relation to each other in the left-and-rightdirection, extends in the front-and-rear direction, and is formed in awired circuit pattern (conductive pattern) in which each of the rear endportions thereof is bent inward in a direction opposed to each other.

Specifically, the pair of electrode wires 6 include a first wire(right-side wire) 6A arranged on the right side (one side in theleft-and-right direction) and a second wire (left-side wire) 6B arrangedin spaced relation on the left side of the first electrode wire 6A (theother side in the left-and-right direction). The rear end portions ofthe pair of electrode wires 6 are connected with an electricalresistance detector 10.

The bridge wire 9 is provided in order to connect the conductive layer4, and, on the upper surface of the insulating layer 2, the bridge wire9 is provided on the inner sides of the pair of electrode wires 6 in theopposed direction. Specifically, the bridge wire 9 is arranged on theinner sides of the pair of electrode wires 6 in the opposed direction inspaced relation thereto and formed in a generally U-shape in plane viewopening toward the front side.

More particularly, the bridge wire 9 integrally includes a firstconnecting wire (right-side connecting wire) 7A arranged on the rightside (one side in the left-and-right direction), a second connectingwire (left-side connecting wire) 7B arranged in spaced relation on theleft side of the first connecting wire 7A (the other side in theleft-and-right direction), and a third connecting wire (rear-sideconnecting wire) 7C for connecting the rear end portions thereof.

A protective layer 15 which covers the electrode pattern 3 and thebridge wire 9 is formed thereon.

The protective layer 15 is directly formed on the surfaces (the upperand side surfaces) of the electrode pattern 3 and the bridge wire 9.

The conductive layers 4 are formed by dividing a layer into plural (two)layers and are spaced apart from each other in the left-and-rightdirection. Each of the conductive layers 4 is formed in a generallyrectangular shape in plane view extending in the front-and-reardirection, and includes a first conductive layer 4A arranged on theright side (one side in the left-and-right direction) and a secondconductive layer 4B arranged in spaced relation on the left side of thefirst conductive layer 4A (the other side in the left-and-rightdirection).

The first conductive layer 4A is provided over the first electrode wire6A and the first connecting wire 7A and covering them. The secondconductive layer 4B is also provided over the second electrode wire 6Band the second connecting wire 7B and covering them.

The conductive layers 4, and the electrode pattern 3 and the bridge wire9 that are covered with the conductive layers 4 constitute a detectionportion 20 for detecting a specific gas in the gas detection sensor 1.

In the detection portion 20, the electrode wire 6 (the first electrodewire 6A or the second electrode wire 6B) of the electrode pattern 3covered with the conductive layers 4 is determined as an electrode 5 (afirst electrode 5A or a second electrode 5B), and the bridge wire 9 (thefirst connecting wire 7A or the second connecting wire 7B) covered witheach of the conductive layers 4 is determined as a connecting portion 8(a first connecting portion 8A or a second connecting portion 8B).

The electrode 5 and the connecting portion 8 are arranged in both endportions of the respective conductive layers 4 in the left-and-rightdirection. Specifically, the first electrode 5A and the first connectingportion 8A are arranged in the right side end portion and the left sideend portion of the first conductive layer 4A, respectively, while thesecond connecting portion 8B and the second electrode 5B are arranged inthe right side end portion and the left side end portion of the secondconductive layer 4B, respectively.

That is, the first conductive layer 4A is connected to the firstelectrode 5A and the first connecting portion 8A, and the secondconductive layer 4B is connected to the second electrode 5B and thesecond connecting portion 8B.

Thus, the conductive layers 4 (the first conductive layer 4A and thesecond conductive layer 4B) are electrically connected with the firstelectrode 5A and the second electrode 5B through the bridge wire 9between the first electrode 5A and the second electrode 5B.

Next, a method for producing the gas detection sensor 1 is describedwith reference to FIG. 3.

In this method, an insulating layer 2 is first prepared, as shown inFIG. 3( a).

As an insulating material for forming the insulating layer 2, forexample, synthetic resin such as a liquid crystal polymer (LCP; apolymer of an aromatic or aliphatic dihydroxy compound, a polymer of anaromatic or aliphatic dicarboxylic acid, a polymer of an aromatichydroxycarboxylic acid, a polymer of an aromatic diamine, an aromatichydroxyamine, or an aromatic aminocarboxylic acid, etc.), polyethyleneterephthalate (PET), polyimide (PI), polyether nitril, polyethersulfone, polyethylene naphthalate, polyphenylene sulfide (PPS),polyether imide (PEI), and polyvinyl chloride is used. These insulatinglayers can be used alone or in combination.

As such insulating material, a material having a low coefficient ofwater absorption, humidity expansion, thermal expansion, and gaspermeability is preferably used.

Among them, a liquid crystal polymer or polyethylene terephthalate ispreferably used. Since a liquid crystal polymer or polyethyleneterephthalate has a low coefficient of water absorption and gaspermeability (oxygen permeability, etc.), the insulating layer 2 can heprevented from swelling due to absorption of water vapor in the ambientair, and the conductive layers 4 can be prevented from being affecteddue to penetrating of gas or water vapor from the undersurface of theinsulating layer 2. Therefore, a detection error caused by the swellingof the insulating layer 2 and a detection error caused by the affectiondue to the penetration from the insulating layer 2 can be prevented.

To prepare the insulating layer 2, for example, a sheet of theabove-mentioned insulating material is prepared. Alternatively, theinsulating layer 2 can be prepared by forming a film of a varnish of aninsulating material on a stripping plate, which is not shown, bycasting, drying the film, and then curing the dried film as required.

Commercially available products can be used as the sheet of theabove-mentioned insulating material, and, examples thereof include aVECSTAR series sheet (a liquid crystal polymer sheet, manufactured byKuraray Co., Ltd.), a BIAC series sheet (a liquid crystal polymer sheet,manufactured by JAPAN GORE-TEX INC.), and a Lumirror series sheet (apolyethylene terephthalate sheet, manufactured by Toray Industries,Inc.).

The insulating layer 2 thus formed has a thickness in the range of, forexample, 5 to 30 μm, or preferably 5 to 25 μm.

Subsequently, in this method, as shown in FIG. 3( b), an electrodepattern 3 and a bridge wire 9 are simultaneously formed on theinsulating layer 2.

As a material for forming the electrode pattern 3 and the bridge wire 9,for example, a conductive material such as copper, nickel, gold, tin,rhodium, solder, or alloys thereof is used. Among them, copper ispreferably used from the viewpoint of conductivity and processability.

The electrode pattern 3 and the bridge wire 9 are formed in the form ofthe above-mentioned pattern by a known patterning method such as aprinting method, an additive method, or a subtractive method.

In the printing method, for example, a paste containing microparticlesof the above-mentioned material is screen-printed on the upper surfaceof the insulating layer 2 in the above-mentioned pattern and thensintered. This directly forms the electrode pattern 3 and the bridgewire 9 on the upper surface of the insulating layer 2.

In the additive method, for example, a thin conductive film (a seedlayer), which is not shown, is first formed on the upper surface of theinsulating layer 2. The thin conductive film is formed by sequentiallylaminating a thin chromium film and a thin copper film by sputtering, orpreferably chromium sputtering and copper sputtering.

A plating resist is then formed on the upper surface of the thinconductive film in a pattern reverse to the pattern of the electrodepattern 3 and the bridge wire 9, and the electrode pattern 3 and thebridge wire 9 are formed on the upper surface of the thin conductivefilm exposed from the plating resist by electrolytic plating.Thereafter, the plating resist and the thin conductive film in theportion on which the plating resist has been laminated are removed.

In the subtractive method, for example, a two-layer substrate (copperfoil two-layer substrate, etc.) on which a conductive layer made of theabove-mentioned conductive material is preliminarily laminated on theupper surface of the insulating layer 2 is first prepared, and a dryfilm resist is then laminated on the conductive layer. Thereafter, thedry film resist is exposed to light and developed. Then, an etchingresist having the same pattern as the above-mentioned pattern of theelectrode pattern 3 and the bridge wire 9 is formed. Subsequently, theconductive layer exposed from the etching resist is subjected tochemical etching (wet etching), and the etching resist is then removedto form the electrode pattern 3 and the bridge wire 9. To prepare thetwo-layer substrate, a known adhesive layer may be interposed betweenthe insulating layer 2 and the conductive layer as required.

In the formation of the electrode pattern 3 and the bridge wire 9 by theabove-mentioned subtractive method, commercially available products canbe used as the copper foil two-layer substrate, and, for example, aliquid crystal polymer copper-clad laminate (ESPANEX L series,single-sided, standard type/P type, manufactured by Nippon SteelChemical Co., Ltd.) in which a conductive layer made of copper ispreliminarily laminated on the upper surface of the insulating layer 2made of liquid crystal polymer is used.

Among these patterning methods, a printing method is preferably used.This method ensures that the electrode pattern 3 and the bridge wire 9can be directly formed on the upper surface of the insulating layer 2,so that a specific gas can be detected with high accuracy.

The electrode pattern 3 and the bridge wire 9 thus formed have athickness in the range of, for example, 5 to 30 μm, or preferably 5 to20 μm.

An electrode wire 6 has a length (length of a first electrode wire 6Aand a second electrode wire 6B in the front-and-rear direction) in therange of, for example, 5 to 100 mm, or preferably 5 to 50 mm, and thebridge wire 9 has a length (length of a first connecting wire 7A and asecond connecting wire 7B in the front-and-rear direction) in the rangeof, for example, 4.5 to 95.0 mm, or preferably 4.5 to 45.0 mm.

The electrode wire 6 has a width (length of the first electrode wire 6Aand the second electrode wire 6B in the left-and-right direction) in therange of, for example, 10 to 500 μm, or preferably 20 to 300 μm. Aspacing D1 (spacing in the left-and-right direction) between theelectrode wires 6 is appropriately selected according to the number ofconductive layers 4 and its width, and is in the range of, for example,1 to 30 mm, or preferably 2 to 10 mm.

The bridge wire 9 has a width (length of the first connecting wire 7Aand the second connecting wire 7B in the left-and-right direction, andlength of a third connecting wire 7C in the front-and-rear direction) inthe range of, for example, 10 to 500 μm, or preferably 20 to 300 μm. Aspacing D2 between the first connecting wire 7A and the secondconnecting wire 7B is in the range of, for example, 0.5 to 10 mm, orpreferably 1 to 5 mm.

The spacing between the electrode pattern 3 and the bridge wire 9 in theleft-and-right direction, specifically, the spacing between the firstelectrode wire 6A and the first connecting wire 7A, and the spacingbetween the second electrode wire 6B and the second connecting wire 7Bare determined by the spacing D1 between the electrode wires 6, thewidth of the first connecting wire 7A and the second connecting wire 7B,and the spacing D2 therebetween.

A spacing D3 (spacing in the front-and-rear direction) between the rearend portion (bending portion) of the electrode wire 6 and the bridgewire 9 (the third connecting wire 7C) is in the range of, for example,0.5 to 10 mm, or preferably 1 to 5 mm.

The formation of the electrode pattern 3 and the bridge wire 9simultaneously forms a pair of electrodes 5 in the electrode pattern 3and a pair of connecting portions 8 in the bridge wire 9.

Subsequently, in this method, as shown in FIG. 3( c), a protective layer15 is formed so as to cover the electrode pattern 3 and the bridge wire9.

As a material for forming the protective layer 15, a metal material suchas gold is used. When the protective layer 15 is formed of a metalmaterial, even if a specific gas to be detected is acid gas, thisprotective layer 15 can reliably prevent the electrode pattern 3 and thebridge wire 9 from corrosion.

The protective layer 15 is formed by a known thin film forming method,such as sputtering and plating such as elcctroless plating orelectrolytic plating, so as to cover the electrode pattern 3 and thebridge wire 9.

The protective layer 15 thus formed has a thickness in the range of, forexample, 0.05 to 3 μm, or preferably 0.5 to 1.5 μm.

Subsequently, in this method, as shown in FIG. 3( d), the conductivelayers 4 are sequentially formed on the insulating layer 2 by dividing alayer into plural layers so as to cover the protective layer 15.

Specifically, the first conductive layer 4A is formed on the insulatinglayer 2 so as to cover the protective layer 15 corresponding to thefirst electrode 5A and the first connecting portion 8A, andsubsequently, the second conductive layer 4B is formed on the insulatinglayer 2 so as to cover the protective layer 15 corresponding to thesecond electrode 5B and the second connecting portion 8B.

The conductive layers 4 are formed from a conductive material which isformed from, for example, a mixture of a conductive particle exhibitingconductivity and a non-conductive substance which swells according tothe type and amount (concentration) of a specific gas.

The conductive particle that may be used includes, for example, anorganic conductor, an inorganic conductor, or a mixed organic/inorganicconductor.

Examples of the organic conductor include conductive polymers such aspolyaniline, polythiophene, polypyrrole, and polyacetylene; carbonaceousmaterials such as carbon blacks, graphite, corks, and C60; and chargetransfer complexes such as tetramethylparaphenylenediamine-chloranile,alkali metal tetracyanoquinolinodimethane complexes, andtetrathiofulvalene halide complexes.

Examples of the inorganic conductor include metals such as silver, gold,copper, and platinum; alloys of the above-mentioned metals such as Au—Cualloys; highly doped semiconductors such as silicon, gallium arsenide(GaAs), indium phosphide (InP), molybdenum sulfide (MoS₂), and titaniumoxide (TiO₂); conductive metal oxides such as indium oxide (In₂O₃), tinoxide (SnO₂), and sodium platinum oxide (NaxPt₃O₄); and superconductorssuch as YBa₂Cu₃O₇ and Tl₂Ba₂Ca₂Cu₃O₁₀.

Examples of the mixed organic/inorganic conductor includetetracyano-platinate complexes, iridium-halocarbonyl complexes, andstacked macrocyclic complexes.

These conductive particles can be used alone or in combination.

The non-conductive substance that may be used includes, for example,non-conductive organic polymers such as main chain carbon polymers, mainchain acyclic heteroatom polymers, and main chain heterocyclic polymers.

Examples of the main chain carbon polymer include polydiene, polyalkene,polyacrylic, polymethacrylic, polyvinyl ether, polyvinyl thioether,polyvinyl alcohol, polyvinyl ketone, polyvinyl halide, polyvinylnitrile, polyvinyl ester, polystyrene, poly (α-methylstyrene),polyarylene, polyvinyl alcohol, and polyvinyl acetate.

Examples of the main chain acyclic heteroatom polymer include polyoxide,polycarbonate, polyester, polyanhydride, polyurethane, polysulfonate,polysiloxane, polysulfide, polythioester, polysulfone, polysulfoneamide, polyamide, polyamide amine (polyamide amine dendrimer), polyurea,polyphosphazene, polysilane, and polysilazane.

Examples of the main chain heterocyclic polymer includes poly(furantetracarboxylic acid diimides), polybenzoxazolcs, polyoxadiazoles,polybenzothiadinophenothiazines, polybenzothiazoles,polypyrazinoquinoxalines, polypyromellitimides, polyquinoxalines,polybenzimidazoles, polyoxindoles, polyoxoisoindolines,polydioxoisoindolines, polytriazines, polypyridazines, polypiperazines,polypyridines, polypiperidines, polytriazoles, polypyrazoles,polypyrrolidines, polycarboranes, polyoxabicyclononanes,polydibenzofurans, polyphthalides, polyacetals, polyvinyl pyrrolidones,and polybisphenols, or other hydrocarbons.

As the non-conductive substance, for example, oligomers such aspolyester acrylate oligomer may also be used.

These non-conductive substances can be used alone or in combination.

To form the conductive layer 4, a coating method such as spraying by anultrasonic spray method, solution casting, air spraying, or dropcoating, is used. Further, for example, a thin-film forming techniquesuch as vacuum vapor deposition, CVD, plasma polymerization, ionizedcluster beam deposition, epitaxial growth, and Langmuir Blodgett (LB) isused.

Preferably, spraying by an ultrasonic spray method is used.

In the spraying by an ultrasonic spray method, a conductivecomponent-containing liquid (solution and/or suspension) containing anorganic solvent, a conductive particle, and a non-conductive substance(or precursors (monomers) thereof) is prepared and then sprayed onto theinsulating layer 2 by an ultrasonic spray method.

The organic solvent having a boiling point of 40 to 120° C. ispreferable, and examples thereof include ketones such as acetone, methylethyl ketone, and methyl isobutyl ketone; alcohols such as methylalcohol, ethyl alcohol, isopropyl alcohol, and n-propyl alcohol;aromatic hydrocarbons such as toluene and xylene; halogenatedhydrocarbons such as a methylene chloride; ethers such astetrahydrofuran (THF); and nitriles such as acetonitrile.

These organic solvents can be used alone or in combination.

In the case of preparing the conductive component-containing liquid as asolution, an organic solvent (solvent) capable of dissolving aconductive particle and a non-conductive substance (or precursorsthereof) is selected as the organic solvent, and such organic solvent ismixed with the conductive particle and the non-conductive substance (orthe precursors thereof) to be dissolved.

Alternatively, in the case of preparing the conductivecomponent-containing liquid as a suspension, an organic solvent(dispersion medium) capable of dispersing a conductive particle isselected as the organic solvent, and the conductive particle issuspended in the organic solvent. In such case, for example, theconductive particle is suspended in the organic solvent with a knownagitator such as a forced agitator or an ultrasonic agitator.

As for the mixing proportions of the respective ingredients to preparethe conductive component-containing liquid, per 100 parts by weight ofthe non-conductive substance, the conductive particle is in the rangeof, for example, 10 to 50 parts by weight, or preferably 20 to 35 partsby weight, and the organic solvent is in the range of, for example, 2000to 20000 parts by weight, or preferably 5000 to 15000 parts by weight.

If desired, known additives such as a catalyst may be added to theconductive component-containing liquid.

The conductive component-containing liquid thus prepared has a viscosity(at 25° C.) in the range of, for example, 1×10⁻⁴ to 0.05 Pa·s, orpreferably 5×10⁴ to 0.01 Pa·s.

The ultrasonic spray method is a spray coating method using anultrasonic wave, for example, in which a liquid is sprayed in the formof a liquid droplet (in mist form) having a fine particle diameter byultrasonic vibration. Thus, a coating solution can be applied to anobject uniformly and effectively.

When the conductive component-containing liquid is sprayed onto theinsulating layer 2 by an ultrasonic spray method, it is sprayed in theform of a liquid droplet having a fine particle diameter. Therefore, theorganic solvent in the conductive component-containing liquid evaporatesby the time when the liquid droplet of the conductivecomponent-containing liquid reaches the insulating layer 2. For thisreason, such ultrasonic spray method can suppress wetting and spreadingof the conductive component-containing liquid. As a result,agglomeration and/or uneven distribution of the conductive material(conductive particle and non-conductive substance) can be suppressed.

In the spraying of the conductive component-containing liquid by theultrasonic spray method, the frequency of the ultrasonic wave is in therange of, for example, 20 to 150 kHz, or preferably 60 to 120 kHz. Whenthe frequency of the ultrasonic wave is within the above-mentionedrange, the sprayed conductive component-containing liquid can have anextremely finer diameter than the liquid droplet obtained by an airspray method.

More specifically, for example, the use of an ultrasonic wave having afrequency of 60 kHz can make the particle diameter of the conductivecomponent-containing liquid approximately 35 μm or less while the use ofan ultrasonic wave having a frequency of 120 kHz can make the particlediameter of the conductive component-containing liquid approximately 20μm or less.

The finer diameter the liquid droplet of the conductivecomponent-containing liquid has, the more uniformly the conductivecomponent-containing liquid can be sprayed onto the insulating layer 2,so that the thickness of the conductive layer 4 thus obtained can bemade more uniform.

Commercially available ultrasonic spray devices can be used to spray theabove-mentioned conductive component-containing liquid onto theinsulating layer 2 by the ultrasonic spray method. As such ultrasonicspray device, for example, an ultrasonic spray nozzle (manufactured bySono-Tek Corporation) is used.

To spray the conductive component-containing liquid onto the insulatinglayer 2, more specifically, for example, an ultrasonic spray device isfirst installed so that its jet opening faces the insulating layer 2,and the conductive component-containing liquid is then sprayed from thejet opening of the ultrasonic spray device onto the insulating layer 2that is, for example, 10 to 200 mm, or preferably 30 to 100 mm spacedapart from the jet opening thereof.

Such spraying allows the organic solvent in the conductivecomponent-containing liquid to well evaporate by the time a jet of theconductive component-containing liquid injected from the jet openingreaches the insulating layer 2.

In such spraying of the conductive component-containing liquid, when theconductive component-containing liquid freely falls as a liquid droplethaving a fine particle diameter, for example, assist gas can beintroduced as required.

Examples of the assist gas include nitrogen, argon, and air, and whenthe nozzle has a diameter of approximately 1 mm, the discharge pressurethereof is in the range of, for example, 0.05 to 5.0 kPa, or preferably0.3 to 1.0 kPa.

For example, a mask may be used to spray the conductivecomponent-containing liquid in a pattern corresponding to the respectiveconductive layers 4. More specifically, before the spraying of theconductive component-containing liquid, the insulating layer 2 iscovered with a mask having an opening formed in a pattern correspondingto a first conductive layer 4A. Subsequently, the conductivecomponent-containing liquid is sprayed from above of the insulatinglayer 2 and the mask onto the insulating layer 2 and the protectivelayer 15 both exposed from the opening in the mask, and the mask is thenremoved. Thus, the first conductive layer 4A is first formed.

Thereafter, the insulating layer 2 on which the first conductive layer4A is formed is covered with a mask having an opening formed in apattern corresponding to a second conductive layer 4B. Subsequently, theconductive component-containing liquid is sprayed from above of theinsulating layer 2 and the mask onto the insulating layer 2 and theprotective layer 15 both exposed from the opening in the mask, and themask is then removed. Thus, the second conductive layer 4B is formed.

Therefore, the conductive component-containing liquid can besequentially sprayed in the patterns corresponding to the respectiveconductive layers 4.

It should be noted that the conductive component-containing liquid issprayed, for example, at room temperature (at approximately 25° C.).

In this way, the respective conductive layers 4 (the first and thesecond conductive layers 4A and 4B) can be sequentially formed byspraying the conductive component-containing liquid onto the insulatinglayer 2 plural times (twice) in sequence.

Here, generally, in the formation of the respective conductive layers 4,for example, when the conductive component-containing liquid is appliedto the insulating layer 2 using a coating method such as solutioncasting, air spraying, or drop coating, the conductivecomponent-containing liquid thus applied may wet-spread over theinsulating layer 2 until it dries. In such case, agglomeration anduneven distribution of the conductive particles may occur duringevaporation of the organic solvent in the conductivecomponent-containing liquid, resulting in difficulty in uniformlyforming the conductive layers 4 each having a predetermined thickness.

However, the spraying by the ultrasonic spray method allows the organicsolvent to evaporate during the spraying. Therefore, wetting andspreading of the conductive component-containing liquid can besuppressed, so that the thickness of the respective conductive layers 4can be made uniform.

Further, in the spraying by the ultrasonic spray method, since theconductive layers 4 are formed by spraying the conductivecomponent-containing liquid, there is no significant loss of theconductive component-containing liquid, which is highly cost effective.

Conductivity may also be imparted to the conductive layers 4 formed inthe above manner by doping (e.g., exposure to iodine) as required.

Each of the conductive layers 4 has a thickness in the range of, forexample, 0.01 to 50 μm, preferably 0.1 to 20 μm, or more preferably 0.2to 10 μm.

Further, each of the conductive layers 4 has a length (length in thefront-and-rear-direction) in the range of, for example, 5 to 95 mm, orpreferably 5 to 45 mm, and has a width (length in the left-and-rightdirection) in the range of, for example, 0.5 to 20 mm, preferably 1 to 5mm. The spacing between the conductive layers 4 (the first and thesecond conductive layers 4A and 4B) is in the range of, for example, 0.5to 10 mm, or preferably 1 to 5 mm. The first conductive layer 4A and thesecond conductive layer 4B have, for example, the same area,specifically, in the range of 2.5 to 1900 mm², or preferably 5 to 225mm²,

Thus, a detection portion 20 including the conductive layers 4, theelectrodes 5, and the connecting portions 8 can be formed.

In the conductive layers 4 in the detection portion 20 thus formed, anelectrical pathway (path) formed of conductive particles between thefirst electrode 5A and the first connecting portion 8A, and between thesecond electrode 5B and the second connecting portion 8B can suffer fromelectrical interference due to a gap formed of non-conductive substance.Such gap of the non-conductive substance provides a predeterminedelectrical resistance to between the first electrode 5A and the firstconnecting portion 8A, and between the second electrode 5B and thesecond connecting portion 8B (between the first and the secondelectrodes 5A and 5B), and the predetermined electrical resistancevaries according to the swelling of the conductive layers 4 due to theabsorption and adsorption of a specific gas to be described later.

In the detection portion 20, the type of the conductive layers 4 may bethe same or different from each other. Further, the gas detection sensor1 is formed as a wired circuit board because it includes the insulatinglayer 2 and an electrode pattern 3 (wired circuit pattern).

Thereafter, as shown in FIG. 1, the rear end portions of a pair ofelectrode wires 6 are connected to the electrical resistance detector10. Thus, the gas detection sensor 1 can be produced.

Next, a method for detecting a specific gas using the gas detectionsensor 1 will be described.

First, in this method, a gas detection sensor 1 is arranged in alocation where a specific gas is desired to be detected.

The specific gas to be detected by the gas detection sensor 1 is notparticularly limited, and examples thereof include organic substancessuch as alkane, alkene, alkyne, allene, alcohol, ether, ketone,aldehyde, carbonyl, and carbanion, derivatives (e.g., halogenatedderivative, etc.) of the above-mentioned organic substances, biochemicalmolecules such as sugar, isoprene, isoprenoid, and chemical substancessuch as a fatty acid and derivatives of a fatty acid.

Thereafter, in this method, an electrical resistance between a firstelectrode 5A and a second electrode 5B in a detection portion 20 isdetected by an electrical resistance detector 10. More specifically,when a specific gas contacts a non-conductive substance of conductivelayers (conductive material) 4, the non-conductive substance absorbs oradsorbs the specific gas and then swells according to the type and/oramount (concentration) of the specific gas. This leads to swelling ofthe conductive layers 4, thereby changing the electrical resistancevalue between the first electrode 5A and the second electrode 5B in theconductive layers 4. Such change in the electrical resistance value isdetected by the electrical resistance detector 10.

By analyzing the detected change in the electrical resistance value by acomputer, which is not shown, having a given library, the specific gasis qualitatively and/or quantitatively analyzed for the type and/oramount (concentration) thereof.

These analyses for the change in the electrical resistance value can beperformed according to the description of Japanese Unexamined PatentPublication No. 11-503231 or U.S. Pat. No. 5,571,401.

In the gas detection sensor 1, the type and amount of the specific gascan be reliably detected in the detection portion 20 by detecting theelectrical resistance value in the conductive layer 4 of which theswelling ratio varies depending on the type and amount of the specificgas, by the electrical resistance detector 10.

The conductive layer 4 is formed by dividing into two layers, a firstconductive layer 4A and a second conductive layer 4B. Therefore, each ofthe first conductive layer 4A and the second conductive layer 4B has asmaller area partitioned than the entire conductive layer 4,specifically, an area of one-half (½) of the total area of the firstconductive layer 4A and the second conductive layer 4B. This partitioncan make the thickness of the first conductive layer 4A and the secondconductive layer 4B even more uniform. Therefore, the thickness of theentire conductive layer 4 can be made uniform.

As a result, the type and amount (concentration) of the specific gas canbe detected with excellent accuracy.

In the gas detection sensor 1, the first conductive layer 4A and thesecond conductive layer 4B, which are formed by dividing into two layersand spaced apart from each other, are connected with each other throughthe bridge wire 9 between the first electrode 5A and the secondelectrode 5B. Therefore, electrical connection between the firstelectrode 5A and the second electrode 5B can be reliably achieved, whichin turn can reliably perform gas detection with high accuracy.

In the above explanation, the gas detection sensor 1 is exemplified andthe specific substance to be detected is described as a gas. The gasdetection sensor of the present invention does not limit the state ofthe substance to be detected and, for example, the specific substance tobe detected may be a liquid.

In the above explanation, two detection portions 20 having twoconductive layers 4 (the first and the second conductive layers 4A and4B) are provided. However, the number of detection portions 20 is notparticularly limited and, for example, three or more detection portionscan be provided, though not shown. Such provision of the detectionportions 20 can achieve detection of the type and amount (concentration)of a specific gas with even higher accuracy.

In the above explanation, in the formation of the conductive layers 4,the first conductive layer 4A and the second conductive layer 4B aresequentially formed. However, for example, they may he formedsimultaneously. When the first conductive layer 4A and the secondconductive layer 4B are simultaneously formed by spraying by anultrasonic spray method, a conductive component-containing liquid issprayed at once using a mask having two openings formed in a patterncorresponding to the first conductive layer 4A and the second conductivelayer 4B.

In this method, the conductive layer 4 can be formed easily in a shorttime.

In the above explanation, the undersurface of the insulating layer 2 isexposed. However, for example, as shown in phantom line in FIG. 2, theundersurface of the insulating layer 2 can be covered with a metal layer18.

The metal layer 18 is formed under the insulating layer 2, and morespecifically, is provided over the entire undersurface of the insulatinglayer 2.

As a metal material for forming the metal layer 18, for example,stainless steel, 42-alloy, aluminum, copper-beryllium, or phosphorbronze is used. Preferably, stainless steel is used from the viewpointof corrosion resistance.

To provide the metal layer 18, for example, the above-mentioned metallayer 18 is preliminarily prepared and then, the insulating layer 2 isformed. Alternatively, the metal layer 18 and the insulating layer 2 canbe prepared as a two-layer substrate on which the metal layer 18 and theinsulating layer 2 are preliminarily sequentially laminated. Furtheralternatively, they can be prepared as a three-layer substrate on whichthe metal layer 18, the insulating layer 2, and a conductive layer (aconductive layer for forming an electrode pattern 3 and a bridge wire 9)are preliminarily sequentially laminated. Commercially availableproducts can be used as the three-layer substrate, and for example, aliquid crystal polymer copper-clad laminate (ESPANEX L series,double-sided, standard type/P type, manufactured by Nippon SteelChemical Co., Ltd.) in which the insulating layer 2 made of liquidcrystal polymer and the conductive layer made of copper arepreliminarily laminated on the surface of the metal layer 18 made ofcopper is used.

The metal layer 18 has a thickness in the range of, for example, 0.05 to50 μm, or preferably 0.1 to 20 μm.

When such metal layer 18 is provided under the insulating layer 2,particularly the insulating layer 2 made of insulating material havinghigh gas permeability, the metal layer 18 can cut off the gas to bebrought into contact with the insulating layer 2 from the underside, sothat the insulating layer 2 can be prevented from swelling due toabsorption of water vapor in the ambient air, and the conductive layer 4can be prevented from being affected due to penetrating of gas and watervapor from the undersurface of the insulating layer 2. Therefore, adetection error caused by the swelling of the insulating layer 2 and adetection error caused by the affection due to the penetration from theinsulating layer 2 can be prevented.

Further, in the above explanation, the protective layer 15 is formed soas to cover the electrode pattern 3 and the bridge wire 9. However, theprotective layer 15 may be formed so as to cover only the electrodes 5and the connecting portions 8 but not to cover the electrode wires 6 andthe connecting wires 7 that are not included in the region of thedetection portion 20,

Furthermore, in the above explanation, the protective layer 15 isformed. However, for example, although not shown, the electrodes 5 andthe conductive layers 4 can be directly formed without forming theprotective layer 15.

FIGS. 4 to 12 show another embodiment of the gas detection sensoraccording to the present invention. The same reference numerals areprovided in the subsequent figures for members corresponding to each ofthose described above, and their detailed description is omitted.

In the above explanation, the conductive layer 4 is divided into twolayers. However, the number of divisions is not particularly limitedand, for example, it may be divided into three (see FIG. 4), or four ormore layers.

In FIG. 4, the conductive layer 4 includes three conductive layers, thatis, the first conductive layer 4A, the second conductive layer 4B, andthe third conductive layer 4C, and the first conductive layer 4A, thethird conductive layer 4C, and the second conductive layer 4B aresequentially arranged from the right side toward the left side.

Further, the bridge wire 9 includes the first bridge wire 9A connectedto the first conductive layer 4A and the third conductive layer 4C, andthe second bridge wire 9B connected to the third conductive layer 4C andthe second conductive layer 4B.

Since each of the first, the second, and the third conductive layers 4A,4B, and 4C that are formed by dividing into three layers as shown inFIG. 4 has a smaller area partitioned than each area of the first andthe second conductive layers 4A and 4B shown in FIG. 1, specifically, anarea of one-third (⅓) of the total area of the first, the second, andthe third conductive layers 4A, 4B, and 4C, the first, the second, andthe third conductive layers 4A, 4B, and 4C can have even more uniformthickness.

Therefore, the thickness of the entire conductive layer 4 can be madeuniform. As a result, the type and amount (concentration) of thespecific gas can be detected with even more excellent accuracy.

More particularly, the total area of the conductive layer 4 ispreliminarily determined, and when such predetermined area is too largeto easily make the thickness uniform, the number of divisions is set tobe increased as described above. Along with this increase, the number ofthe bridge wire 9 is increased. Specifically, when the total area of theconductive layer 4 is, for example, 40 mm², the number of divisions isset to two or more, or when it is, for example, 60 mm², the number ofdivisions is set to three or more.

In the above explanation, the bridge wire 9 is formed in a generallyU-shape in plane view. However, the shape thereof is not limited. Forexample, it can be formed in a generally rectangular shape in plane view(FIG. 5), in a generally rectangular frame shape in plane view (FIGS. 6and 7), or in a generally H-shape in plane view (FIG. 8).

In FIG. 5, the bridge wire 9 is formed in the shape of a thin flatsheet.

In the gas detection sensor 1, since the bridge wire 9 is formed in aflat plate shape, the resistance between the first conductive layer 4Aand the second conductive layer 4B can be reduced. Moreover, the bridgewire 9 can effectively prevent a broken wire, thereby improving theyield of the gas detection sensor 1. Further, the bridge wire 9 having aflat plate shape can support the insulating layer 2, resulting instabilization of the size of the gas detection sensor 1.

In FIG. 6, the bridge wire 9 further includes a fourth connecting wire(a front-side connecting wire) 7D which connects between the front endportions of the first and the second connecting wires 7A and 7B.

In FIG. 7, the bridge wire 9 is formed in a generally H-shape in planeview opening toward both the front side and the rear side, and furtherincludes a fifth connecting wire 7E which connects between the midpointsof the first and the second connecting wires 7A and 7B in thefront-and-rear-direction. The fifth connecting wire 7E extends in theleft-and-right direction.

In FIG. 8, the bridge wire 9 integrally includes the first connectingwire 7A, the second connecting wire 7B, and a sixth connecting wire(cross wire) 7F. The sixth connecting wire (cross wire) 7F connectsbetween the midpoints of the first and the second connecting wires 7Aand 7B in the front-and-rear-direction, and is formed so as to extend inthe left-and-right direction.

In the above explanation, the bridge wire 9 is provided. However, forexample, as shown in FIGS. 9 and 10, the first conductive layer 4A andthe second conductive layer 4B can be connected without providing thebridge wire 9.

In FIGS. 9 and 10, the first conductive layer 4A and the secondconductive layer 4B are in contact with each other on the left end faceof the first conductive layer 4A and the right end face of the secondconductive layer 4B. Thus, the first conductive layer 4A and the secondconductive layer 4B are electrically connected with each other.

In the gas detection sensor 1, there is no need to provide the bridgewire 9, so that the configuration can be simplified. Besides, theabsence of the bridge wire 9 eliminates the need to consider theresistance in the bridge wire 9, which can ensure gas detection witheven higher accuracy.

In the formation of the first and the second conductive layers 4A and 4Bof FIGS. 9 and 10, when these two layers are sequentially formed bydividing, the right side end edge of the second conductive layer 4B mayoverlap on the left side end edge of the first conductive layer 4A asshown in FIGS. 11 and 12. In such case, the bridge wire 9 ispreliminarily formed and thereafter, the first conductive layer 4A andthe second conductive layer 4B arc sequentially formed.

In the conductive layer 4, a portion (overlapping portion) 14overlapping the left side end edge of the first conductive layer 4A andthe right side end edge of the second conductive layer 4B is usuallyformed so as to extend in the front-and-rear direction.

The bridge wire 9 is connected to the first conductive layer 4A and thesecond conductive layer 4B which are adjacent in the left-and-rightdirection so that the first connecting wire 7A and the second connectingwire 7B sandwich the overlapping portion 14 in the left-and-rightdirection.

In the gas detection sensor 1, when the overlapping portion 14 is formedin the conductive layer 4, the thickness of the conductive layer 4 inthe overlapping portion 14 becomes thicker than that of its surrounding.This makes the swelling ratio of the non-conductive substance in theoverlapping portion 14, caused by absorption or adsorption of gas duringgas detection, higher than that of the non-conductive substance aroundthe overlapping portion 14. Therefore, the change in the electricalresistance value in the overlapping portion 14 becomes larger than thechange in the electrical resistance value around the overlapping portion14. Further, when the bridge wire 9 is not provided, an electricalpathway (path) between the first electrode 5A and the second electrode5B is formed so as to pass through the overlapping portion 14.

Therefore, a significant change in the electrical resistance valuecaused by the overlapping portion 14 is detected by the electricalresistance detector 10, which may deteriorate the accuracy of the gasdetection.

However, in the gas detection sensor 1 of FIGS. 11 and 12, even if theoverlapping portion 14 is formed in the conductive layer 4, the bridgewire 9 is provided. Therefore, the path between the first electrode 5Aand the second electrode 5B is formed so as to bypass the overlappingportion 14 and pass through the third connecting wire 7C. At the sametime, the first conductive layer 4A and the second conductive layer 4Bare reliably connected by the first connecting wire 7A and the secondconnecting wire 7B of the bridge wire 9, respectively, through the thirdconnecting wire 7C. As a result, gas detection can be ensured with highaccuracy.

EXAMPLE

While in the following, the present invention is described in furtherdetail with reference to Examples and Comparative Example, the presentinvention is not limited to any of them.

(Production of Gas Detection Sensor)

Example 1

A liquid crystal polymer copper-clad laminate (product number: ESPANEXL-12-25-00NE, single-sided, standard type, manufactured by Nippon SteelChemical Co., Ltd.) in which a 12 μm-thick copper foil as a conductivelayer was preliminarily laminated on the upper surface of a 25 μm-thickliquid crystal polymer sheet as an insulating layer was prepared, and anelectrode pattern and a bridge wire having the above-mentioned patternwere simultaneously formed by a subtractive method (see FIGS. 1 and 3(b)).

Each of the first and the second electrode wires had a length of 20 mmand a width of 0.25 mm, and a spacing (D1) between the first and thesecond electrode wires was 5 mm. The bridge wire had a width of 0.25 mm,each of the first and the second connecting wires had a length of 19 mm,and a spacing (D2) therebetween was 2.5 mm. Each of a spacing betweenthe first electrode wire and the first connecting wire and a spacingbetween the second electrode wire and the second connecting wire was 1.3mm, and a spacing (D3) between the rear end portion of the electrodewire and the third connecting wire was 1 mm.

Then, a 0.5 μm-thick gold layer serving as a protective layer was formedon surfaces of the electrode pattern and the bridge wire (see FIG. 3(c)).

Subsequently, 40 mg of carbon black (Black pearl 2000), 150 mg ofpolyvinyl alcohol, and 20 mL of THF were blended and mixed to prepare aconductive component-containing liquid.

The conductive component-containing liquid thus obtained was thensprayed onto the insulating layer using an ultrasonic spray nozzle(AccuMist Nozzle, manufactured by Sono-Tek Corporation) through a maskhaving an opening (opening area of 30 mm²) formed in a rectangular shapein plane view of a 1.67 mm width (length in the left-and-rightdirection) and a 18 mm length (length in the front-and-rear-direction)(see FIG. 3( d)).

More particularly, the conductive component-containing liquid wassprayed in twice. Specifically, first, the insulating layer was coveredwith the above-mentioned mask so that the opening was opposed to theright side of the insulating layer, and the conductivecomponent-containing liquid was then sprayed in a pattern correspondingto the first conductive layer. Subsequently, the mask was moved to theleft side, the insulating layer was covered with the mask so that theopening was opposed to the left side of the insulating layer, and theconductive component-containing liquid was sprayed in a patterncorresponding to the second conductive layer. By doing this, the firstconductive layer and the second conductive layer were sequentiallyformed by dividing.

To spray the conductive component-containing liquid, the frequency ofthe ultrasonic wave was set to 60 kHz, and an assist gas (air gas, adischarge pressure of 0.4 kPa, and a nozzle diameter of approximately 1mm) was introduced at 25° C. The distance from the distal end of theultrasonic spray nozzle to the insulating layer was 4 cm.

Example 2

The gas detection sensor was produced in the same manner as in Example 1except that two bridge wires were formed in place of one bridge wire,and that three conductive layers (a first conductive layer, a secondconductive layer, and a third conductive layer) were formed in place oftwo conductive layers (the first and the second conductive layers) (seeFIG. 4).

Incidentally, the spacing (D2) between the first connecting wire and thesecond connecting wire in each of the bridge wires was 1.65 mm, and eachof the spacing between the first electrode wire and the first connectingwire of the first bridge wire, the spacing between the second electrodewire and the second connecting wire of the second bridge wire, and thespacing between the second connecting wire of the first bridge wire andthe first connecting wire of the second bridge wire was 1.3 mm.

Further, the conductive component-containing liquid was sprayed threetimes. A mask having an opening (opening area of 20 mm²) formed in arectangular shape in plane view of a 1.11 mm width (length in theleft-and-right direction) and an 18 mm length (length in thefront-and-rear-direction) was used during the spraying.

Example 3

The gas detection sensor was produced in the same manner as in Example 2except that the shape of the bridge wire was changed from a generallyU-shape in plane view to the shape of a thin flat sheet (see FIG. 5).

Incidentally, the bridge wire was formed so that its outer shape was thesame as the outer peripheral edge of the bridge wire in Example 2.

Comparative Example 1

The gas detection sensor was produced in the same manner as in Example 1except that the electrode pattern was not provided and that oneconductive layer was continuously formed in place of two conductivelayers (the first and the second conductive layers) (see FIG. 13).

Incidentally, in the spraying of the conductive component-containingliquid, a mask having an opening (opening area of 60 mm²) formed in arectangular shape in plane view of a 3.33 mm width (length in theleft-and-right direction) and a 18 mm length (length in thefront-and-rear-direction) was used to form conductive layers at once.

(Evaluation)

(Resistance Between Electrodes)

A resistance value between the first electrode and the second electrodein the gas detection sensor produced according to each of Examples andComparative Example was repeatedly measured 10 times with an ohm tester.The results are shown in Table 1.

(Sensor Function)

The gas detection sensor produced in each of Examples and ComparativeExample was exposed to a gas (steam) atmosphere containing ethanol gasat a known concentration and the ethanol gas in the atmosphere wasdetected.

As a result, the ethanol gas at the known concentration was able to bedetected by the gas detection sensors of Examples 1 to 3 and ComparativeExample 1. After the gas detection was repeated 5 times to measure theethanol gas, the results showed that the gas detection sensors ofExamples 1 to 3 had a lower dispersion (standard deviation) than the gasdetection sensor of Comparative Example 1.

[Table 1]

TABLE 1 Ex./Comp. Ex. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1 Area of EachConductive Layer (mm²) 30 20 20 60 Area of Entire Conductive Layer (mm²)60 60 60 60 Resistance Value Standard Deviation 3 1.3 1.3 5 BetweenFirst Average Value (kΩ) 21.8 21.2 21.2 19.3 Electrode and Maximum Value(kΩ) 27 23 23 30 Second Electrode Minimum Value (kΩ) 13 19 19 10

While the illustrative embodiments of the present invention are providedin the above description, such is for illustrative purpose only and itis not to be construed limitative. Modification and variation of thepresent invention which will be obvious to those skilled in the art isto be covered by the following claims.

What is claimed is:
 1. A substance detection sensor comprising: aninsulating layer; two electrodes spaced in opposed relation to eachother on the insulating layer; a conductive layer formed between the twoelectrodes on the insulating layer so as to electrically connect the twoelectrodes, and of which a swelling ratio varies depending on at leastone of the type or amount of a specific gas, the conductive layer beingdivided into plural conductive layers arranged side-by-side on theinsulating layer; and wires for connecting the plural conductive layers,wherein the plural conductive layers comprise an overlapping portionconstituted by overlapping side edge portions of respective adjacentconductive layers, and wherein the wires are connected to the respectiveadjacent conductive layers so as to sandwich the overlapping portion.